Atmospheric Burner for Gas Log Fireplace Producing Stage Combustion and Yellow Chemiluminescent Flame

ABSTRACT

An atmospheric burner assembly for a gas log fireplace comprises a mixing chamber adapted to receive gas from a gas supply and mix gas and air therein. The burner assembly also comprises a manifold adapted to receive gas from a gas supply. The burner assembly also has a burner with a first port communicating with the mixing chamber and a second port communicating with the manifold. The second port is adapted to generate a flame pattern that is embedded within the first port. When installed in the fireplace, the burner assembly combusts pure gas at the second port for rich combustion and a mixture of gas and air at the first port for lean combustion, thereby promoting stage combustion at the burner assembly and producing a yellow chemiluminescent flame.

BACKGROUND

The disclosure relates generally to gas burner systems, and specifically to gas burner systems for open flame display, such as gas logs for fireplaces, and even more specifically gas burner systems for vent free or direct vent applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an embodiment of the burner assembly comprising a top plate with six dual port burners with a portion of the top plate being partially broken away to show further detail of an interior of the burner assembly that includes a mixing chamber with ceramic pellets disposed therein that supplies a gas-air mixture to lean flame burner ports of the dual port burners of the burner assembly and a receiver comprising a manifold assembly that delivers gas to rich flame burner ports of the dual port burners of the burner assembly;

FIG. 2 is a perspective view of an underside of a top plate of the burner assembly of FIG. 1, showing additional detail of the manifold assembly used to deliver gas to the rich flame burner ports of the dual port burners of the burner assembly; and

FIG. 3 is a schematic diagram of a fireplace in which the burner assembly is installed showing additional detail of valves and orifices used in connection with the manifold and receiver to vary the flow of gas to the lean and the rich flame burner ports of the dual port burners of the burner assembly.

DETAILED DESCRIPTION

Referring to the figures, a gas burner assembly is generally designated by the reference numeral 10 in FIG. 1, and generally comprises a box shape with top plate 12 and a base 14 spaced from the top plate to form a mixing chamber 16 therebetween. Attached to the periphery of the base 14 are front and back walls 18,20 that partially enclose the burner assembly leaving the left and right sides open for piping and an air intake associated with the burner assembly. It should be appreciated that the directions top, bottom, left, right, front, and back are used merely for illustrative purposes as they correspond to the general orientation shown in the drawings, and the directions top, bottom, left, right, front, and back are not intended to be limiting in any sense to a specific orientation or structure. Preferably, the top plate 12 and the base 14 are generally flat and the walls 18,20 are perpendicular to the top plate and the base so that the burner assembly 12 takes the shape of a rectangular solid for ease of construction. However, sloped walls, a curved base, or other convenient shapes could be used as desired to form the burner assembly 10. Preferably, the top plate, front and back sides, and base are made of metal or other material that can endure prolonged intense heat as well as the frequent cycling between temperature extremes. Ceramic materials may also be used for forming the top plate, base, and/or front and back sides.

As shown in the FIGS. 1 and 2, six dual port burners 30 are located in the burner assembly top plate 12, as will be described in greater detail below. A pilot for ignition of the burner assembly may be provided, and carryover holes 34 are arranged in lines extending across the top plate in a random pattern to carry the flame after ignition across the burner assembly top plate 12 to ignite the dual port burners 30. As best shown in FIG. 3, a log support, grate, or other convenient support 36 may be disposed above the top plate 12 for supporting log materials 38, and material 40 resembling burning embers, such steel or rock wool or spun glass, is preferably piled under the grate or log support around and atop the burner top plate 12 over the carry-over holes 34. The grate may also be formed integral with the burner assembly top plate and the logs held in place with pins extending from the top plate.

A gas delivery system 50 (FIG. 3) connects the burner assembly 10 to an external combustible gas source, including but not limited to natural gas and propane (“LP”). The gas delivery system 50 carries gas (or feed) from the external source through a main cut-off valve 52 to a “tee” connection 54 where a first portion of the gas is directed to a receiver 56 for eventual delivery to rich flame burner ports associated with each dual port burner 30, and second portion of the gas is delivered to the mixing chamber 16 via a main gas manifold 58 to be mixed with air for eventual delivery to the carry over holes 34 and lean flame burner ports associated with each dual port burner 30. In the mixing chamber 16, the gas and air is mixed in order to produce a lean flame zone with highly efficient combustion and reduced emissions of NO_(x) and CO. Preferably, the air to gas ratio/mixture developed in the mixing chamber 16 to be combusted in the lean flame zone is between about five (5) percent and about thirty (30) percent more than the stoichiometric air to gas ratio mixture needed for complete combustion. The rich flame zone at the rich flow burner has an air to gas ratio/mixture that is theoretically or about zero. During the combustion process at the dual port burner 30, the average air to gas ratio/mixture reaches a fuel rich environment creating higher theoretical flame temperature and taller flames. The higher theoretical flame temperature produces more heat. The receiver 56 preferably receives between about five (5) and about thirty (30) percent of the gas flow while the main gas manifold 58 receives between about seventy (70) and ninety-five (95) percent of the gas flow. The percentage of gas flow may be regulated by orifices 60. Valves, orifices and/or the pipe size associated with each of the receiver (including tube branches 68 extending from the spider manifold, as will be explained below) and main gas manifold may also be used in combination to regulate and apportion flow to the main gas manifold, and the receiver and the tube branches. As shown by example in FIGS. 1 and 2, the receiver 56 preferably comprises a spider manifold with the tube branches 68 extending therefrom to each of the dual port burners 30. The receiver 56 is preferably disposed under the burner top plate 12 in the mixing chamber 16. The main gas manifold may connect to a side of the burner assembly and discharge directly into the mixing chamber 16. Valves and controls associated with the valves may be disposed under the bottom support to protect them from the heat of the fireplace. While the gas delivery system 50 is shown in FIG. 3 as a single pipe with the “tee” connection 54 to the receiver 56 and the main gas manifold 58, it is understood that multiple pipes could be used to deliver the gas to the receiver or main gas manifold or mixing chamber, and that the pipe(s) could enter the burner assembly through the front and/or back sides, or even the base for connection to the receiver or main gas manifold.

The burner assembly mixing chamber 16 may contain ceramic pellets 70 (FIG. 1) comprising a conglomeration of particles sufficiently disparate in size and/or shape to form a loosely packed permeable barrier for the gas to flow through. The ceramic pellets 70 may completely fill the mixing chamber 16 or only a portion of it. The irregularity of the ceramic particles diffuses the gas so that the gas is mixed and dispersed in the mixing chamber prior to being directed to the carry over holes 34 and/or the lean flame burner port(s) of the dual port burners 30, where it is ignited and combusted. The use of ceramic pellets in the mixing chamber reduces the occurrence of flash-back or flame extinction problems when the burner system is turned on or off. Because of the diffuse gas flow that reaches the burners at different rates and times, the combustion flames at the burners “dances” much like a woodburning flame.

Each dual port burner 30 of the burner assembly comprises a lean flame burner port 80 and a rich flame burner port 82. As shown by example in FIGS. 1 and 2, the lean flame burner port 80 comprises a plurality of slots in the top plate arranged in a pattern communicating with the mixing chamber, and the rich flame burner port 82 comprises a distal end of the tube branch 68 extending from the receiver or spider manifold 56. The rich flame burner port 82 combusts pure gas to produce a rich flame, i.e., a yellow flame, and solid state C₂. The lean flame burner port 80 combusts the gas/air mixture from the mixing chamber 16 and the C₂ produced by the rich flame zone thereby producing a yellow flame and providing an aesthetically pleasing simulation of wood burning in a conventional fireplace. Additionally, burning the C₂ and the soot particle, which were produced in the rich flame zone, inside the lean flame zone increases the heat output of the fireplace unit, as a higher theoretical flame temperature is achieved for the fireplace unit. Further, burning the C₂ and the soot particle, which were produced in the rich flame zone, inside the lean flame zone, tends to increase flame height. Preferably, the rich flame burner port 82 produces a flame pattern that is embedded within a flame pattern produced by the lean flame burner port 80, thus allowing the C₂ produced by the rich flame burner port to be introduced directly into the flame pattern of the lean flame burner port, thereby reducing potential emissions and excess soot deposits. As shown in FIG. 1, the rich flame and lean flame burner ports 82,80 of each dual port burner 30 are aligned such that the lean flame burner port surrounds and is co-axially aligned with the rich flame burner port. The distal end of the tube branch 68 may be positioned in the center of the slot pattern of the lean flame burner port as one method of embedding the rich flame burner port flame pattern within the lean flame burner port flame pattern. The opening forming the rich flame burner port may be dimensioned to correspond to a #55 drill size. It should be appreciated that the rich flame burner port may also be spaced from and/or arranged at an angle relative to the lean flame burner port in such a way that the flame pattern produced by the rich flame burner port impinges or is embedded within the flame pattern produced by the lean flame burner port. To increase flame height, each dual port burner may be provided with a flame venturi 84 comprising an upstanding wall enclosing the lean flame burner port. As shown in FIG. 3, the flame venturi extends around the periphery of the slot pattern of the lean flame burner port. Holes 86 may be provided in the upstanding wall of the flame venturi to draw additional combustion air into the lean flame burner port 80 and to accelerate the flame upward from the burner 30.

As shown in FIG. 3, a valve 90 may be positioned in the gas supply preferably between the “tee” connection 54 and the receiver or spider manifold 56 to control a rate of gas flow to the rich flame burner ports 82 and thus the rate of rich flame combustion. The valve 90 may throttle the flow or secure the flow, as may be desired. The valve 90 may be manually actuated or operatively connected to a control 92 that automatically sets the position of the valve for a specific operation or function. The control 92 may comprise a microprocessor unit on the fireplace that integrates and controls some or all of the functions the fireplace. The control 92 may also be operated via remote controls associated with the fireplace. For instance, to assist in the generation of a “dancing flame,” the control 92 may dynamically cycle the valve 90 to vary the flow rate of gas to the receiver or spider manifold 56. The control's dynamic cycle may be based upon a timer, or ambient conditions in the area in which the gas-log fireplace is situated, for instance, room temperature or sound. The control 92 may also be operatively connected to or interfaced with a thermostatic control associated with the gas-log fire place for automatic or manual temperature control based upon ambient conditions. The control may also be selectively controlled by the user, as may be desired, to increase, decrease “yellow” flame height, change flame color, change temperature, or to suspend the “yellow” flame appearance by stopping rich flame combustion. The control 92, and/or other valves (not shown) provided in addition to the orifices 60 in the any of the connections to the main gas manifold and spider manifold, may be used for fine tuning of the combustion process for a specific configuration at set-up or installation of the fire place, for instance, to fine tune operations for direct vent and vent-less configurations, high altitude installations, and/or LP and natural gas applications.

Use of stage combustion increases the heat output of the fireplace for a given gas usage. For instance, by producing higher theoretical flame temperature, stage combustion generates the heat of a 38,000 BTU unit while only expending the gas of a 28,000 BTU unit, thus allowing smaller units to be used and/or conservation of gas.

It should be appreciated the dual port burner may comprise an arrangement other than the plate arrangement shown in the drawings. For instance, the dual port burner may comprise coaxially aligned tubes with the lean flame port comprising an outer tube communicating with the mixing chamber and the rich flame port comprising an inner tube disposed in the outer tube communicating with the receiver. As a further example as shown in FIGS. 1, 2, and 3, lean flame burner port may comprise an tube extension 100 projecting away from the top plate in register with a hole 102 in the top plate 12 that communicates with the mixing chamber, and the spider manifold tube branch 68 may be lengthened to extend through the top plate inside the tube extension 100 so that the distal ends of the tube extension and tube branch are elevated from the top plate thereby allowing combustion and flame generation to be elevated relative to the top plate. As shown by example in FIG. 3, the tube extension 100 and lengthened tube branch 68 may extend through an aperture 104 in a log of the log set 38 to simulate burning logs in positions elevated from the top plate.

While specific embodiments have been described in detail in the foregoing detailed description and illustrated in the accompanying drawings, those with ordinary skill in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof. 

1. An atmospheric burner assembly for a gas log fireplace comprising: a mixing chamber adapted to receive gas from a gas supply and mix gas and air therein; a receiver adapted to receive gas from a gas supply; and a burner with a first port communicating with the mixing chamber and a second port communicating with the receiver, the second port being adapted to generate a flame pattern that is embedded with a flame pattern of the first port, wherein when installed in the fireplace, the burner assembly combusts gas at the second port for rich combustion and a mixture of gas and air at the first port for lean combustion, thereby promoting stage combustion at the burner assembly and producing a yellow chemiluminescent flame.
 2. The atmospheric burner assembly of claim 1, wherein: the first burner port surrounds the second burner port.
 3. The atmospheric burner assembly of claim 1, wherein: the mixing chamber comprises a generally planar burner plate spaced from a burner assembly bottom support.
 4. The atmospheric burner assembly of claim 3, wherein: the first burner port comprises slots formed in a pattern in the burner plate.
 5. The atmospheric burner assembly of claim 4, wherein: the second port burner port comprises an opening in a tube communicating with the receiver arranged within the slot pattern.
 6. The atmospheric burner assembly of claim 1, wherein: the receiver is disposed in the mixing chamber.
 7. The atmospheric burner assembly of claim 1, wherein: the receiver is configured to draw between about 5% and 30% of gas supplied to the burner assembly.
 8. A gas log fireplace comprising: a gas supply; a mixing chamber in communication with the gas supply adapted to mix gas and air therein; a receiver in communication with the gas supply; and a burner with a first port communicating with the mixing chamber and a second port communicating with the receiver, the second port being adapted to generate a flame pattern that is embedded within a flame pattern generated by the first port, the burner combusting gas at the second port for rich combustion and a mixture of gas and air at the first port for lean combustion, thereby promoting stage combustion and producing a yellow chemiluminescent flame at the burner.
 9. The fireplace of claim 8, wherein: the first burner port and the second burner port are co-axially aligned.
 10. The fireplace of claim 8, wherein: the mixing chamber comprises a generally planar burner plate spaced from burner assembly bottom support.
 11. The fireplace of claim 10, wherein: the first port comprises slots formed in a pattern in the burner plate.
 12. The fireplace of claim 11, wherein: the second port comprises an opening in a tube communicating with the receiver arranged within the slot pattern.
 13. The fireplace of claim 8, wherein: the receiver is disposed in the mixing chamber.
 14. The fireplace of claim 8, wherein: the receiver is configured to draw between about 5% and about 30% of gas supplied to the burner.
 15. The fireplace of claim 8, further comprising: a valve positioned between the gas supply and the receiver.
 16. The fireplace of claim 14, further comprising: a user control operatively connected to the valve adapted to selectively control a level of gas flow from the gas supply to the receiver.
 17. The fireplace of claim 16, wherein: the user control is adapted to supply to the receiver between 0% and about 30% of the gas supplied to the burner.
 18. A gas log fireplace comprising: a gas supply; a burner assembly comprising a generally planar burner plate spaced from a burner bottom support and forming a mixing chamber receiving gas from the gas supply and mixing the gas with air therein, the burner assembly having a manifold disposed in the mixing chamber receiving gas from the gas supply, the burner plate having a plurality of slot patterns formed therein, each slot pattern being spaced from another slot pattern in the burner plate, slots in the slot pattern communicating with the mixing chamber and combusting the mixture of gas and air for lean combustion, the manifold having a plurality of tubes extending therefrom to areas adjacent the slot patterns, the tubes having openings arranged within the slot pattern, the openings of the tubes combusting pure gas for rich combustion, the burner assembly generating stage combustion and producing a yellow chemiluminescent flame.
 19. The fireplace of claim 18, wherein: the manifold is configured to draw between about 5% and about 30% of gas supplied to the burner assembly.
 20. The fireplace of claim 18, further comprising: a valve positioned between the gas supply and the manifold.
 21. The fireplace of claim 20, further comprising: a user control operatively connected to the valve adapted to selectively control a level of gas flow from the gas supply to the manifold.
 22. The fireplace of claim 21, wherein: the user control is adapted to supply to the manifold between 0% and about 30% of the gas supplied to the burner assembly. 